possible fix for gmodule link error on some environments (#74). Updated copyright year.
differentiate DNS lookup error from connection errors.
added SOCKS4/5 proxy support.
session.c: remove idle callback on close, and check GSource in the callback (possibly fixes crashes on cancellation).
merged from LibSylph branch.
made workaround for state machine freeze problem in Win32.
fixed compilation failure on some environments.
session_read_data_as_file_cb(): don't write to file until buffer is filled more than the half.
reduced memory usage on POP3 session.
reduced memory usage on SMTP session.
changed the license of LibSylph from GPL to LGPL.
made some core modules library (libsylph).